HR: 15:45h
AN: U33A-08    [Abstracts]
TI: Impact-generated Hydrothermal Activity at the Chicxulub Crater
AU: * Kring, D A
EM: kring@lpi.usra.edu
AF: Lunar and Planetary Institute, 3600 Bay Area Blvd., Houston, TX 77058, United States
AU: Zurcher, L
EM: lzurcher@email.arizona.edu
AF: Lowell Program in Economic Geology, University of Arizona, 1040 E. Fourth St., Tucson, AZ 85721, United States
AU: Abramov, O
EM: abramovo@boulder.swri.edu
AF: Southwest Research Institute, 1050 Walnut St., Suite 400, Boulder, CO 80302, United States
AB: Borehole samples recovered from PEMEX exploration boreholes and an ICDP scientific borehole indicate the Chicxulub impact event generated hydrothermal alteration throughout a large volume of the Maya Block beneath the crater floor and extending across the bulk of the ~180 km diameter crater. The first indications of hydrothermal alteration were observed in the crater discovery samples from the Yucatan-6 borehole and manifest itself in the form of anhydrite and quartz veins. Continuous core from the Yaxcopoil-1 borehole reveal a more complex and temporally extensive alteration sequence: following a brief period at high temperatures, impact- melt-bearing polymict breccias and a thin, underlying unit of impact melt were subjected to metasomatism, producing alkali feldspar, sphene, apatite, and magnetite. As the system continued to cool, smectite-series phyllosilicates appeared. A saline solution was involved. Stable isotopes suggest the fluid was dominated by a basinal brine created mostly from existing groundwater of the Yucatan Peninsula, although contributions from down-welling water also occurred in some parts of the system. Numerical modeling of the hydrothermal system suggests circulation occurred for 1.5 to 2.3 Myr, depending on the permeability of the system. Our understanding of the hydrothermal system, however, is still crude. Additional core recovery projects, particularly into the central melt sheet, are needed to better evaluate the extent and duration of hydrothermal alteration.
DE: 3616 Hydrothermal systems (0450, 1034, 3017, 4832, 8135, 8424)
DE: 5220 Hydrothermal systems and weathering on other planets
DE: 5420 Impact phenomena, cratering (6022, 8136)
SC: Union [U]
MN: 2007 Joint Assembly